Three-phase slurry reactors are well known to those skilled in the art. In operation, the reactor comprises a slurry zone and a freeboard zone. In the slurry zone solid catalyst particles are kept in suspension in a liquid. The liquid serves as heat-transfer medium. The mixture of catalyst particles and liquid is commonly referred to as slurry. One or more gaseous reactants bubble through the slurry zone. The freeboard zone located above the slurry zone contains substantially no slurry and serves as a disengagement zone between slurry, and gaseous products and reactants.
The catalyst particles are typically kept in suspension by stirring or agitation by a mechanical device or, preferably, by an upward gas and/or liquid velocity.
Although substantially all catalyst particles are present in the slurry zone, a proportion of the catalyst particles escape from the slurry zone into the freeboard zone and may stick to the reactor wall or internals in the freeboard zone. In the absence of liquid heat-transfer medium, but in the presence of unreacted gaseous reactants, the said catalyst particles continue to catalyse the exothermic reaction. In this way, local hot spots are created which may damage the reactor vessel and/or internals.
Accordingly, it would be desirable to be able to remove catalyst particles efficiently from the freeboard zone.
For the purposes of this specification the term catalyst particles is intended as reference to catalyst particles per se and/or any fines thereof.